feat(052): runtime-neutral KNX connector

[lxsaah]

Wave B of design 052, third and last connector. The adapter owns the UDP socket and the clock; this crate owns the tunnelling protocol.

tokio_client.rs (632) and embassy_client.rs (473) are gone, along with the whole Tokio*/Embassy* alias set. One KnxConnector<B, D, N> wires both runtimes onto the client::connection_task that landed in wave A.

With this, all three connectors carry zero runtime modules and zero unsafe impls.

Breaking

• KnxConnector::new(binder, delay, gateway_url, &CHANNELS) — generic over core's DatagramBinder and Delay.
• KnxConnector::tokio(gateway_url) on a host: supplies the Tokio transports and its channels, so a caller needs only the URL.
• with_command_queue_size becomes the const generic N. An embassy_sync::Channel is sized at compile time — an MCU allocates it in a static, where the size must be a constant.
• KnxConnectorBuilder, KnxConnectorImpl and the Tokio*/Embassy* aliases are gone.

Updated in-tree: aimdb-codegen, both KNX demos, and topic_provider_tests.

Worth a look in review

The channels are a caller-supplied &'static Channels<N>. Both the connection task and the pumps are spawned as 'static futures, so the channels must outlive the connector. An MCU supplies them from a StaticCell; KnxConnector::tokio leaks one pair at build — bounded, once per process, matching design 037's allocate-at-build model, but a deliberate leak worth seeing.

D1 moved into this PR. codegen-drift runs in make check, and aimdb-codegen emitted KnxConnector::new(&knx_gateway) — a signature that no longer exists. KnxConnector::tokio exists so the generated line stays one call rather than adapter types plus a static; codegen changed by one word and no re-baseline was needed (✓ Codegen output compiles against the workspace).

aimdb-tokio-adapter becomes a tokio-runtime dependency, the same relaxation taken for the serial connector — the adapter owns the datagram socket on both runtimes rather than the connector duplicating it.

Two adapter binders gained Clone. TokioUdpBinder and EmbassyUdpBinder could not be held by a ConnectorBuilder, which clones its transport per build. That is the third wave-A type to need this after the TCP dialers — the traits were right, but their composition into a builder was untested. Worth a compile-time assertion in core.

Verification

make check clean: 2 017 tests, 0 failures, all stages including codegen-drift.

Note

Touches examples/embassy-knx-connector-demo/src/main.rs, which #251 also edits (its SerialServer line). Whichever merges second needs a rebase there.